Quadrature communications device with power combiner and related methods

ABSTRACT

A communications device may include In-phase (I) power amplifiers configured to generate I amplified signals, Quadrature (Q) power amplifiers configured to generate Q amplified signals, an I controller coupled to the I power amplifiers and configured to selectively enable some of the I power amplifiers, and a Q controller coupled to the Q power amplifiers and configured to selectively enable some of the Q power amplifiers. The communications device may also include a power combiner configured to combine the I amplified signals and the Q amplified signals in a combined amplified signal, and an antenna coupled to the power combiner.

TECHNICAL FIELD

This application relates to the field of communications, and moreparticularly, to wireless communications systems and related methods.

BACKGROUND

Cellular communication systems continue to grow in popularity and havebecome an integral part of both personal and business communications.Cellular telephones allow users to place and receive phone calls mostanywhere they travel. Moreover, as cellular telephone technology isadvanced, so too has the functionality of cellular devices. For example,many cellular devices now incorporate Personal Digital Assistant (PDA)features such as calendars, address books, task lists, calculators, memoand writing programs, etc. These multi-function devices usually allowusers to wirelessly send and receive electronic mail (email) messagesand access the Internet via a cellular network and/or a wireless localarea network (WLAN), for example.

Cellular devices have radio frequency (RF) processing circuits andreceive or transmit radio communications signals typically usingmodulation schemes. Constant envelope signals use phase modulation torepresent/encode information; however, their amplitude does not changewith time. In contrast, non-constant envelope modulation schemes encodeinformation in amplitude and phase and are typically generated usingquadrature transmit paths (I/Q paths). There are several amplitudemodulation schemes, such as 8 phase-shift keying (8PSK) used in secondgeneration cellular transceivers, quadrature phase-shift keying (QPSK)used in third generation cellular transceivers, and orthogonalfrequency-division multiplexing (OFDM) used in fourth generationcellular transceivers, all typically generated using a quadraturetransmitter. In contrast to constant envelope modulation, quadraturemodulation and demodulation circuits may create linearity issues withpower amplifiers because the peak power transmitted is higher thanaverage power, and therefore the PA is mostly operated in the“backed-off” condition, where it is inefficient. This drawback may befurther exacerbated under the condition of poor antenna match. This cancause some degradation of total radiated power (TRP) and raise harmonicinterference issues because of the greater non-linearity of a poweramplifier.

In particular, cellular devices that use Quadrature modulations circuitsmay experience difficulty in transmitting large bandwidth signals, forexample, third and fourth generation cellular transceiver signals. Inparticular, the large bandwidth of these signals may demand a fairlylinear amplifier, which may prove to be quite power inefficient, therebyhurting battery life.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of an example embodiment of acommunications device.

FIG. 2 is a detailed schematic block diagram of the communicationsdevice of FIG. 1.

FIG. 3 is a detailed schematic block diagram of another embodiment ofthe communications device of FIG. 1.

FIG. 4 is a schematic block diagram of an example embodiment of acommunications device.

FIG. 5 is a detailed schematic block diagram of the communicationsdevice of FIG. 4.

FIG. 6 is a detailed schematic block diagram of another embodiment ofthe communications device of FIG. 4.

FIG. 7 is a schematic block diagram of an example embodiment of acommunications device.

FIG. 8 is a detailed schematic block diagram of the communicationsdevice of FIG. 7.

FIG. 9 is a detailed schematic block diagram of another embodiment ofthe communications device of FIG. 7.

FIG. 10-13 are diagrams illustrating a simulation of the communicationsdevice of FIG. 1.

FIG. 14 is a schematic block diagram illustrating example components ofa mobile wireless communications device that may be used with thecommunications devices of FIGS. 1-9.

FIG. 15 is a schematic block diagram of another embodiment of thecommunications device of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present description is made with reference to the accompanyingdrawings, in which embodiments are shown. However, many differentembodiments may be used, and thus the description should not beconstrued as limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete. Like numbers refer to like elements throughout, and primenotation is used to indicate similar elements or steps in alternativeembodiments.

One aspect of the present disclosure is directed to a communicationsdevice. The communications device may comprise an In-phase (I) poweramplifier configured to generate an I amplified signal, a Quadrature (Q)power amplifier configured to generate a Q amplified signal, an Idigital-to-analog converter (DAC) configured to generate an I signal,and a Q DAC configured to generate a Q signal. The communications devicemay also comprise an I power supply circuit coupled to the I poweramplifier and to the I DAC and configured to cause the I power amplifierto modulate an I carrier signal into the I amplified signal based uponthe I signal, a Q power supply circuit coupled to the Q power amplifierand to the Q DAC and configured to cause the Q power amplifier tomodulate a Q carrier signal into the Q amplified signal based upon the Qsignal, and at least one antenna coupled to the I and Q poweramplifiers.

For example, in some embodiments, the communications device may includea power combiner coupled between the I and Q power amplifiers and theantenna. In other embodiments, the communications device may include anI antenna and a Q antenna respectively coupled to the I and Q poweramplifiers. More specifically, the I and Q antennas may be physicallyseparated. Advantageously, the I and Q power amplifiers may beconfigured to operate in a saturated mode of operation.

In some embodiments, the communications device may further comprise an Ilook-up table (LUT) module upstream of the I DAC and configured tosupply a linear I signal thereto, and a Q LUT module upstream of the QDAC configured to supply a linear Q signal. Additionally, thecommunications device may further comprise a phase locked loop (PLL)configured to generate the I and Q carrier signals. The PLL may beconfigured to generate the I and Q carrier signals comprising constantenvelop I and Q carrier signals, for example.

Moreover, in some embodiments, the communications device may furtherinclude an I pre-amplifier coupled between the PLL and the I poweramplifier, and a Q pre-amplifier coupled between the PLL and the Q poweramplifier. The communications device may further comprise at least oneof a 90/270-degree phase shifter and a 0/180-degree phase shifterbetween the PLL and the Q pre-amplifier. Also, the I and Q power supplycircuits may each comprise a respective switched mode power supplycircuit.

For example, the I and Q antennas may comprise rectangular-shaped stripantennas, and the I and Q rectangular-shaped strip antennas may beadjacent to each other. The I and Q DACs may be operable using at leastfourth generation cellular wireless signals.

Another aspect is directed to a method of operating a communicationsdevice. The method may include using an I power amplifier to generate anI amplified signal, using a Q power amplifier to generate a Q amplifiedsignal, using an I DAC to generate an I signal, and using a Q DAC togenerate a Q signal. The method also may include using an I power supplycircuit to cause the I power amplifier to modulate an I carrier signalinto the I amplified signal based upon the I signal, using a Q powersupply circuit to cause the Q power amplifier to modulate a Q carriersignal into the Q amplified signal based upon the Q signal, and using aleast one antenna to transmit the I and Q amplified signals.

Yet another aspect of the present disclosure is directed to anothercommunications device. This communications device may include aplurality of I power amplifiers configured to respectively generate aplurality of I amplified signals, a plurality of Q power amplifiersconfigured to respectively generate a plurality of Q amplified signals,a plurality of I antennas respectively coupled to the plurality of Ipower amplifiers, and a plurality of Q antennas respectively coupled tothe plurality of Q power amplifiers. This communications device may alsoinclude an I controller coupled to the plurality of I power amplifiersand configured to selectively enable at least one of the plurality of Ipower amplifiers, and a Q controller coupled to the plurality of Q poweramplifiers and configured to selectively enable at least one of theplurality of Q power amplifiers.

In some embodiments, the communications device may further comprise an IDAC configured to generate an I bias current signal for the plurality ofI power amplifiers, and a Q DAC configured to generate a Q bias currentsignal for the plurality of Q power amplifiers. Moreover, in theseembodiments, the communications device may further comprise an I LUTmodule upstream of the I DAC and configured to supply a linear I signalthereto, and a Q LUT module upstream of the Q DAC and configured tosupply a linear Q signal thereto.

In other embodiments, the I controller may be configured to cause theplurality of I power amplifiers to modulate an I carrier signal into theplurality of I amplified signals based upon an I digital basebandsignal. Moreover, the Q controller may also be configured to cause theplurality of Q power amplifiers to modulate a Q carrier signal into theplurality of Q amplified signals based upon a Q digital baseband signal.

For example, each I and Q antenna may comprise a respectiverectangular-shaped strip antenna, and the pluralities of I and Qrectangular-shaped strip antennas may be adjacent to each other.

Another aspect is directed to a method of operating a communicationsdevice. The method may include using a plurality of I power amplifiersto respectively generate a plurality of I amplified signals, and using aplurality of Q power amplifiers to respectively generate a plurality ofQ amplified signals. The method may also include using an I controllerto selectively enable at least one of a plurality of I power amplifiers,and using a Q controller to selectively enable at least one of aplurality of Q power amplifiers.

Another aspect of the present disclosure is directed to a communicationsdevice. This communications device may include a plurality of I poweramplifiers configured to respectively generate a plurality of Iamplified signals, a plurality of Q power amplifiers configured togenerate a plurality of Q amplified signals, an I controller coupled tothe plurality of I power amplifiers and configured to selectively enableat least one of the plurality of I power amplifiers, and a Q controllercoupled to the plurality of Q power amplifiers and configured toselectively enable at least one of the plurality of Q power amplifiers.This communications device may also include a power combiner configuredto combine the plurality of I amplified signals and the plurality of Qamplified signals in a combined amplified signal, and an antenna coupledto the power combiner.

In some embodiments, the communications device may further comprise an IDAC configured to generate an I bias current signal for the plurality ofI power amplifiers, and a Q DAC configured to generate a Q bias currentsignal for the plurality of Q power amplifiers. These embodiments of thecommunications device may further comprise an I LUT module upstream ofthe I DAC and configured to supply a linear I signal thereto, and a QLUT module upstream of the Q DAC and configured to supply a linear Qsignal thereto.

Other embodiments of the communications device may include the Icontroller being configured to cause the plurality of I power amplifiersto modulate an I carrier signal into the plurality of I amplifiedsignals based upon an I digital baseband signal. Moreover, the Qcontroller may configured to cause the plurality of Q power amplifiersto modulate a Q carrier signal into the plurality of Q amplified signalsbased upon a Q digital baseband signal. The communications device mayfurther comprise a phase locked loop (PLL) configured to generate the Iand Q carrier signals. The PLL may be configured to generate the I and Qcarrier signals comprising constant envelop I and Q carrier signals.

Another aspect is directed to a method of operating a communicationsdevice. The method may also include using a plurality of I poweramplifiers to respectively generate a plurality of I amplified signals,using a plurality of Q power amplifiers to generate a plurality of Qamplified signals, and using an I controller to selectively enable atleast one of the plurality of I power amplifiers. The method may alsoinclude using a Q controller to selectively enable at least one of theplurality of Q power amplifiers, using a power combiner to combine theplurality of I amplified signals and the plurality of Q amplifiedsignals in a combined amplified signal, and using an antenna to transmitthe combined amplified signal.

Example communications devices may include portable or personal mediaplayers (e.g., music or MP3 players, video players, etc.), remotecontrols (e.g., television or stereo remotes, etc.), portable gamingdevices, portable or mobile telephones, smartphones, tablet computers,etc.

Referring now to FIG. 1, a communications device 20 according to thepresent disclosure is now described. The communications device 20illustratively includes an I power amplifier 22 configured to generatean I amplified signal, a Q power amplifier 21 configured to generate a Qamplified signal, an I DAC 26 configured to generate an I signal, and aQ DAC configured to generate a Q signal. The I and Q DACs 25-26 may beoperable using third or fourth generation cellular wireless signals, forexample, Long Term Evolution (LTE), Mobile WiMAX (IEEE 802.16e-2005),etc. Of course, as will be appreciated by those skilled in the art,other next generation signals may be implemented in the communicationsdevice 20 with appropriate modification.

The communications device 20 illustratively includes an I power supplycircuit 24 coupled to the power amplifier 22 and to the I DAC 26 andconfigured to cause the I power amplifier to modulate an I carriersignal into the I amplified signal based upon the signal. Thecommunications device 20 illustratively includes a Q power supplycircuit 23 coupled to the Q power amplifier 21 and to the Q DAC 25 andconfigured to cause the Q power amplifier to modulate a Q carrier signalinto the Q amplified signal based upon the Q signal. The I and Q powersupply circuits 23-24 effect the modulation by varying a power supplyvoltage used by the I and Q power amplifiers 21-22.

Also, the communications device 20 illustratively includes an I antenna28 coupled to the I power amplifier 22, and a Q antenna 27 coupled tothe Q power amplifier 21. More specifically, the I and Q antennas 28, 27are illustratively physically separated but adjacent to each other, forexample, spaced parallel to each other and at 100 μm apart. The antennas28, 27 are kept close together such that the radiation pattern aroundthem is as desired when the two operate simultaneously, one radiating Ipath RF and the second radiating the Q path RF. For example, the I and Qantennas 27-28 are illustratively rectangular-shaped strip antennas thatare adjacent to each other. Of course, in other embodiments, the I and Qantennas 27-28 may have other shapes.

In other words, the combination of the amplified I and Q signals occursover-the-air and not upstream the antenna as in typical communicationsdevices. Advantageously, the combination medium of air is quitefavorable since it is a linear medium with high dynamic range. Moreover,since the I and Q carrier signals are constant envelop signals, the Iand Q power amplifiers 21-22 may operate in a saturated operation mode,which is energy efficient, rather than the linear mode, as in thetypical communications device. Indeed, in the typical communicationsdevice, a linear mode amplifier may be required to successfully transmitthe wideband third and fourth generation wireless cellular signals.Unfortunately, this leads to undesirably low battery life. In thedisclosed communications device 20, the battery life is advantageouslylengthened due to power amplifier efficiency.

Referring now to FIG. 2, the communications device 20 illustrativelyincludes a transceiver integrated circuit (IC) 41. With the exception ofthe I and Q power supply circuits 23-24, the I and Q power amplifiers21-22, and the I and Q antennas 27-28, the transceiver IC 41 providesthe processing resources for all other components of the communicationsdevice 20.

The communications device 20 illustratively includes an I LUT module 44upstream of the I DAC 26 and configured to supply a linear I signalthereto, and a Q LUT module 43 upstream of the Q DAC 25 configured tosupply a linear Q signal. The I and Q LUT modules 43-44 ensure that theapplied digital modulation signal is represented linearly at the supplyvoltage of the I and Q power amplifiers 21-22 as it goes through the Iand Q DACs 25-26, the reference input of the I and Q power supplycircuits 23-24 (which are illustratively shown as switched mode powersupplies DC-DC (SMPS)), and then to the voltage supplied to the I and Qpower amplifiers. As would be appreciated by the skilled person, theoutput power versus reference input voltage of the illustrated SMPS Iand Q power amplifiers 21-22 is not linear. Hence, the I and Q LUTmodules 43-44 provide the necessary translation (look-up &interpolation/extrapolation) so that the output power is a linearfunction of the DAC code applied at the input of the LUT respectivemodule.

Moreover, in some embodiments, envelope tracking of the digital basebandI and Q signals may be implemented using the I and Q power supplycircuits 23-24. As will be appreciated by the skilled person, thecommunications device 20 may include a pair of duplexers (not shown) forproviding a full duplex transceiver.

The I and Q LUT modules 43-44 are used to linearize the output powerversus the digital baseband I and Q signals. This is accomplished usingcalibration. In particular, the digital baseband I signal is swept andthe output power is measured. The LUT entries are determined such thatthe transfer characteristics of digital input to output power arelinear.

Additionally, the communications device 20 illustratively includes a PLL40 configured to generate the I and Q carrier signals. The PLL 40 may beconfigured to generate the I and Q carrier signals comprising constantenvelop I and Q carrier signals, for example. More specifically, the PLL40 illustratively includes a phase frequency detector (PFD) 38, a lowpass filter 36 downstream therefrom, a signal generator 35 (e.g., avoltage controller oscillator (VCO)) downstream therefrom, and afrequency divider 37 coupled between the signal generator and the PFD.

Moreover, in the illustrated embodiment, the communications device 20illustratively includes an I pre-amplifier 32 coupled upstream the Ipower amplifier 22, and a Q pre-amplifier 31 coupled upstream the Qpower amplifier 21. The communications device 20 illustratively includesa 90-degree phase shifter 33 coupled between the PLL 40 and the Qpre-amplifier 31, and a 0 degrees phase shifter 34 coupled between thePLL 40 and the I pre-amplifier 32. The communications device 20 alsoillustratively includes a serial port module 30 coupled to the I powersupply circuit 24. In the illustrated SMPS embodiment, the serial portmodule 30 is used to control the operating characteristics of the I andQ power supply circuits 23-24 and to exercise programmability offered bythe SMPS, such as internal BW control etc. or switching between PWM andPFM modes etc. as deemed appropriate by the software running in theprocessor in the transceiver or the baseband processor.

Moreover, as will be appreciated by those skilled in the art, the VCO(signal generator 35) may be operated at 2× or even 4× the carrierfrequency, and one or more frequency dividers 37 may be used to dividethe frequency to the specified carrier frequency. This is done to helpthe transceiver IC 41 fight frequency pulling where the high outputpower at the I and Q power amplifiers 21-22 centered as the carrierfrequency couples to the VCO and corrupts the phase noise.

An advantage of such frequency division is that all four phases 0°, 90°,180° and 270° of the RF carrier are readily available. Since the powercan only be positive, the I and Q DACs 25-26 can only provide a positivesignal to the I and Q power supply circuits 23-24, which can onlyproduce a voltage between ground and V_(BATT). Hence, in contrast to atypical up-conversion mixer that may allow positive and negativebaseband input voltage, this communications device 20 does not directlyallow negative inputs.

The way to accommodate the negative I DAC 26 input is to choose 180°phase and to apply the inverted carrier to the I power amplifier 22input. Hence, positive I DAC values apply 0° phase to the I poweramplifier 22 input, and negative I DAC values apply 180° phase to the Ipower amplifier input. Similarly, positive Q DAC values apply 90° phaseto the Q power amplifier 21 input, and negative Q DAC values apply 270°phase to the Q power amplifier input. This is done by using the sign bitto control a multiplexer (FIG. 15) that allows one or the other phase ofthe carrier signal to the I and Q power amplifier 21-22 inputs. Hence,one multiplexer is needed for I path and the second for Q path. Themagnitudes of I DAC and Q DAC values are always positive and, therefore,are applied to the respective DACs 25-26.

In FIG. 2, it is assumed that the 0-degrees phase shifter 34 provides 0°or 180° phase shifting based upon the sign of the I DAC input to I poweramplifier 22, and the 90-degrees phase shifter 33 provides 90° or 270°phase shifting based upon the sign of Q DAC input to Q power amplifier21. The phase shifter 34 can be implemented using a multiplexer withinputs 0° or 180° and the sign bit of I DAC input choosing 0° phase forpositive inputs and 180° phase for negative inputs. Similarly, the phaseshifter 33 can be implemented using inputs 90° and 270° from the PLL 40going into a second multiplexer with 90° selected when Q DAC input ispositive and 270° when it is negative. Of course, this variation of thephase shifters may also be applicable to the PLL circuits in otherembodiments disclosed herein.

In other embodiments, 2× or 4× rate VCO 35 outputs can be divided todirectly obtain the four needed phases. More specifically, instead ofgenerating the 90°/270° and 180° degree phases, the VCO 35 in the PLL 40may be designed at 2× or 4× or even higher frequency and its outputdivided to obtain the needed four phases 0°, 90°, 180° and 270° neededin accordance with quadrature up-conversion. Phase 0° or 180° PLLoutputs are applied to the I power amplifier 22, and the sign of Isignal determines the selection between 0° and 180°.

Referring now to FIG. 3, another embodiment of the communications device20 is now described. In this embodiment of the communications device20′, those elements already discussed above with respect to FIGS. 1-2are given prime notation and most require no further discussion herein.This embodiment differs from the previous embodiment in that thecommunications device 20′ exchanges the separate I and Q antennas for asingle antenna 28′, and further includes a power combiner 42′ coupledbetween the antenna and the I and Q power amplifiers 21′-22′. Moreover,this communications device 20′ illustratively includes I and Qcontrollers 45′-46′ coupled upstream of respective I and Q LUT modules43′-44′ for selecting the desired phase shift for the respective phaseshifters 33′-34′.

Referring briefly and additionally to FIG. 15, another embodiment of thecommunications device 20 is now described. In this embodiment of thecommunications device 20″, those elements already discussed above withrespect to FIG. 3 are given double prime notation and most require nofurther discussion herein. This embodiment differs from the previousembodiment in that the communications device 20″ includes a pair ofmultiplexers 47″-48″ coupled upstream of the I and Q power amplifiers21″-22″ for selectively providing the phase shifted and I and Q signals,as discussed hereinabove.

Referring now to FIG. 4, another embodiment of a communications device50 is now described. This communications device 50 illustrativelyincludes a plurality of I power amplifiers 52 a-52 b configured torespectively generate a plurality of I amplified signals, a plurality ofQ power amplifiers 51 a-51 b configured to respectively generate aplurality of Q amplified signals, a plurality of I antennas 54 a-54 brespectively coupled to the plurality of I power amplifiers, and aplurality of Q antennas 53 a-53 b respectively coupled to the pluralityof Q power amplifiers.

The communications device 50 illustratively includes an I controller 56coupled to the plurality of I power amplifiers 52 a-52 b and configuredto selectively enable at least one of the plurality of I poweramplifiers, and a Q controller 55 coupled to the plurality of Q poweramplifiers 51 a-51 b and configured to selectively enable at least oneof the plurality of Q power amplifiers. In particular, the I and Qcontrollers 55-56 enable as many power amplifiers 51 a-52 b as needed tosuccessfully transmit the signal. For example, fewer power amplifiers 51a-52 b would be enabled when the communications device is near a networktower. Because of this selective enabling of the power amplifiers 51a-52 b, power-added efficiency (PAE) versus power output isadvantageously high. Those skilled in art will appreciate that thecommunications device 50 acts as an effective DAC that produces anelectromagnetic output power directly controlled by the I and Qcontrollers 55-56. This effective DAC can also be called adigital-to-electromagnetic converter (DEC).

Of course, as will be appreciated by the skilled person, the illustratedembodiment includes two I and two Q power amplifiers 51 a-51 b, butother embodiments may include varying numbers, which may depend on thedesired application. For example, the communications device 50 mayinclude 50 I power amplifiers and 50 Q power amplifiers, each generating20 mW of power for a total maximum potential power output of 2 W.Advantageously, since the power output of each power amplifier 41 a-52 bis reduced, the power amplifiers may be provided by a single transceiverchip along with the other signal processing elements, rather than beingoff-chip.

In another example, a 10-bit DEC can be designed by placing 1024pre-power amplifiers and associated antenna segments. The digitalcontrol signal now directly selects the output power produced. Asdescribed above, the sign bit of the digital signal can be used to flipthe carrier signal at the pre-power amplifiers inputs by 180°. Thepre-power amplifier segments can be constructed using similar techniquesused to build typical current source based DACs and usingbinary-to-thermometer encoding to select the pre-power amplifiers. Thoseskilled in the art can appreciate a wide range of typical DACs that candirectly be applied in this embodiment to DECs.

Referring now to FIG. 5, the communications device 50 illustrativelyincludes an I DAC 58 configured to generate an I bias current signal forthe plurality of I power amplifiers 52 a-52 c, and a Q DAC 57 configuredto generate a Q bias current signal for the plurality of Q poweramplifiers 51 a-51 c. In other words, the bias currents to the poweramplifiers 51 a-52 c are manipulated to effect the modulation of the Iand Q carrier signals.

Moreover, in the illustrated embodiment, the communications device 50includes an I LUT module 78 upstream of the I DAC 58 and configured tosupply a linear I signal thereto, and a Q LUT module 79 upstream of theQ DAC 57 and configured to supply a linear Q signal thereto. The I and QLUT modules 78-79 are configured similarly to those of the embodimentsof FIGS. 2-3.

Additionally, the communications device 50 illustratively includes a PLL70 configured to generate the I and Q carrier signals. The PLL 70 may beconfigured to generate the I and Q carrier signals comprising constantenvelop I and Q carrier signals, for example. More specifically, the PLL70 illustratively includes a phase frequency detector (PFD) 71, a lowpass filter 72 downstream therefrom, a signal generator 73 downstreamtherefrom, and a frequency divider 74 coupled between the signalgenerator and the PFD.

Moreover, in the illustrated embodiment, the communications device 50illustratively includes an I driver 64 coupled upstream the I poweramplifiers 52 a-52 c, and a Q driver 63 coupled upstream the Q poweramplifiers 51 a-51 c. The communications device 50 illustrativelyincludes a 90-degree phase shifter 61 coupled between the PLL 70 and theQ driver 63, and a 0 degrees phase shifter 62 coupled between the PLL 70and the I driver 64. As described above, the phase shifters 61-62 can beimplemented by designing the VCO 73 at 2× or 4×RF carrier frequency anddividing the frequency down to obtain the carrier frequency. Using signbit of DAC input and 2:1 multiplexer, these phase shifters 61-62 can beeasily implemented as described earlier. Also, the communications deviceillustratively includes I and Q matching networks 66 a-66 c, 65 a-65 crespectively coupled between the I and Q antennas 54 a-54 c, 53 a-53 cand the I and Q power amplifiers 52 a-52 c, 51 a-51 c. The I and Qmatching networks 66 a-66 c, 65 a-65 c may be programmable andcontrolled digitally for antenna tuning, i.e. varying voltage standingwave ratio (VSWR) at the antenna load.

Indeed, in some embodiments (not shown), the output of the poweramplifiers 51 a-52 b can be parasitically coupled, down-converted andanalog-to-digital (ADC) converted in the small signal IC. Alternatively,a trace close to the antennas 53 a-54 c can pick up the signal and feedit back into the small signal IC where it is down-converted either usinga receiver or a log-Amp followed by an ADC. The tuning elements formatching can be controlled to provide desirable tuning for output powerunder varying VSWR at the antenna 53 a-54 c.

Referring now to FIG. 6, another embodiment of the communications device50 is now described. In this embodiment of the communications device50′, those elements already discussed above with respect to FIGS. 4-5are given prime notation and most require no further discussion herein.This embodiment differs from the previous embodiment in that thecommunications device 50′ does not include the I and Q DACs and LUTmodules. Rather, in this embodiment, the I and Q power amplifiers 51a′-52 c′ are manipulated to modulate the I and Q carrier signals via theI and Q controllers 55′-56′. In other words, the I controller 56′ isconfigured to cause the plurality of I power amplifiers 52 a′-52 c′ tomodulate an I carrier signal into the plurality of I amplified signalsbased upon an I digital baseband signal, and the Q controller 55′ isconfigured to cause the plurality of Q power amplifiers 51 a′-51 c′ tomodulate a Q carrier signal into the plurality of Q amplified signalsbased upon a Q digital baseband signal. In particular, thecommunications device 50′ forms an effective DAC, and the sign of theDAC input controls the appropriate phase carrier to be selected, similarto as described for earlier embodiments. The digital value is convertedto magnitude and controls the number of devices that are turned on. Inthis embodiment of a DEC, the antenna segment is a part of the effectiveDAC.

Referring now to FIG. 7, another embodiment of a communications device80 is now described. This communications device 80 illustrativelyincludes a plurality of I power amplifiers 84 a-84 b configured torespectively generate a plurality of I amplified signals, a plurality ofQ power amplifiers 83 a-83 b configured to generate a plurality of Qamplified signals, an I controller 82 coupled to the plurality of Ipower amplifiers and configured to selectively enable at least one ofthe plurality of I power amplifiers, and a Q controller 81 coupled tothe plurality of Q power amplifiers and configured to selectively enableat least one of the plurality of Q power amplifiers. This communicationsdevice 80 illustratively includes a power combiner 85 configured tocombine the plurality of I amplified signals and the plurality of Qamplified signals in a combined amplified signal, and an antenna 86coupled to the power combiner.

Referring now to FIG. 8, the communications device 80 illustrativelyincludes an I DAC 102 configured to generate an I bias current signalfor the plurality of I power amplifiers 84 a-84 c, and a Q DAC 101configured to generate a Q bias current signal for the plurality of Qpower amplifiers 83 a-83 c. In other words, the bias currents to thepower amplifiers 83 a-84 c are manipulated to effect the modulation ofthe I and Q carrier signals.

Moreover, in the illustrated embodiment, the communications device 80includes an I LUT module 104 upstream of the T DAC 102 and configured tosupply a linear I signal thereto, and a Q LUT module 103 upstream of theQ DAC 101 and configured to supply a linear Q signal thereto. The I andQ LUT modules 103-104 are configured similarly to those of theembodiments of FIGS. 2-3.

Additionally, the communications device 80 illustratively includes a PLL93 configured to generate the I and Q carrier signals. The PLL 93 may beconfigured to generate the I and Q carrier signals comprising constantenvelop I and Q carrier signals, for example. More specifically, the PLL93 illustratively includes a phase frequency detector (PFD) 94, a lowpass filter 95 downstream therefrom, a signal generator 97 downstreamtherefrom, and a frequency divider 96 coupled between the signalgenerator and the PFD.

Moreover, in the illustrated embodiment, the communications device 80illustratively includes an I driver 88 coupled upstream the I poweramplifiers 84 a-84 c, and a Q driver 87 coupled upstream the Q poweramplifiers 83 a-83 c. The communications device 80 illustrativelyincludes a 90-degree phase shifter 91 coupled between the PLL 93 and theQ driver 87, and a 0 degrees phase shifter 92 coupled between the PLL 93and the I driver 88. Also, the communications device 80 illustrativelyincludes I and Q capacitors 86 a-86 c, 85 a-85 c respectively coupledbetween the power combiner 85 and the I and Q power amplifiers 84 a-84c, 83 a-83 c, each of the capacitors being coupled to a groundpotential. As described above, the phase shifters 91-92 can beimplemented by designing the VCO 97 at 2× or 4×RF carrier frequency anddividing the frequency down to obtain the carrier frequency. Using signbit of DAC input and 2:1 multiplexer, these phase shifters 91-92 can beeasily implemented as described earlier.

Referring now to FIG. 9, another embodiment of the communications device80 is now described. In this embodiment of the communications device80′, those elements already discussed above with respect to FIGS. 7-8are given prime notation and most require no further discussion herein.This embodiment differs from the previous embodiment in that thecommunications device 80′ does not include the I and Q DACs and LUTmodules. Rather, in this embodiment, the I and Q power amplifiers 83a′-84 c′ are manipulated to modulate the I and Q carrier signals via theI and Q controllers 81′-82′. In other words, the I controller 82′ isconfigured to cause the plurality of I power amplifiers 84 a′-84 c′ tomodulate an I carrier signal into the plurality of I amplified signalsbased upon an I digital baseband signal, and the Q controller 81′ isconfigured to cause the plurality of Q power amplifiers 83 a′-83 c′ tomodulate a Q carrier signal into the plurality of Q amplified signalsbased upon a Q digital baseband signal.

The I and Q controllers 81′-82′ operate similarly to those of theembodiment described above in FIG. 6. This embodiment here differs fromthe DEC described above in that each DAC element now only drives asegment of the power combiner 85′ and produces an RF output. Hence, itis more appropriately an effective digital-to-RF (D-RF) converter.

Typical methods can be used to build the power combiner 85′, which canbe implemented as a transformer with many primaries and a singlesecondary that drives the antenna 86′. It is beneficial to combine theoutput power passively to keep the output power combination very linear.Passive N:1 combiner structures can be employed; one D-RF converterelement drives one combiner element at its input. The D-RF converter canbe implemented using typical techniques used to build DACs, such asarraying carefully to reduce the impact of INL and DNL, binary tothermometer coding, shuffling the row-column decoders ofbinary-to-thermometer encoder using barrel shifters to implement dynamicelement matching, employing dynamic weighted averaging etc.

Referring now to FIGS. 10-13, a simulation of the efficacy of thetransmission characteristics of the communications device 20 describedin FIGS. 1-2 is now described. Diagram 110 shows the combination of theamplified I and Q signals over the air while chart 120 illustrates the Iand Q waveforms emitted by the I and Q antennas 27-28. The chart 120shows that one wave travels slightly more than the other with thedistance shown as |l₂−l₁|.

With reference to diagram 130, the formula:|l ₂ −l ₁|=|√{square root over ((r cos(φ)+d/2)² +r ² sin²(φ))}{squareroot over ((r cos(φ)+d/2)² +r ² sin²(φ))}−√{square root over ((rcos(φ)−d/2)² +r ² sin²(φ))}{square root over ((r cos(φ)−d/2)² +r ²sin²(φ))}|is illustrated. If r=kd, the formula resolves to:=|√{square root over (r ² +d ²/4+rd cos(φ))}−√{square root over (r ² +d²/4−rd cos(φ))}|

The plot of |l₂−l₁| is shown in diagram 140 of FIG. 13. At 2 GHz and 150mm away from the antenna, the experienced IQ imbalance is 2.4*d degrees,where d is measured in mm. The IQ imbalance due to separate antennas canbe made less than the IQ imbalance floor of the transmitter by keepingthe two antennas very close, thereby enabling successful receipt of theover-the-air combined I and Q signal.

Example components of a mobile wireless communications device 1000 thatmay be used in accordance with the above-described embodiments arefurther described below with reference to FIG. 14. The device 1000illustratively includes a housing 1200, a keyboard or keypad 1400 and anoutput device 1600. The output device shown is a display 1600, which maycomprise a full graphic liquid crystal display (LCD). Other types ofoutput devices may alternatively be utilized. A processing device 1800is contained within the housing 1200 and is coupled between the keypad1400 and the display 1600. The processing device 1800 controls theoperation of the display 1600, as well as the overall operation of themobile device 1000, in response to actuation of keys on the keypad 1400.

The housing 1200 may be elongated vertically, or may take on other sizesand shapes (including clamshell housing structures). The keypad mayinclude a mode selection key, or other hardware or software forswitching between text entry and telephony entry.

In addition to the processing device 1800, other parts of the mobiledevice 1000 are shown schematically in FIG. 14. These include acommunications subsystem 1001; a short-range communications subsystem1020; the keypad 1400 and the display 1600, along with otherinput/output devices 1060, 1080, 1100 and 1120; as well as memorydevices 1160, 1180 and various other device subsystems 1201. The mobiledevice 1000 may comprise a two-way RF communications device having dataand, optionally, voice communications capabilities. In addition, themobile device 1000 may have the capability to communicate with othercomputer systems via the Internet.

Operating system software executed by the processing device 1800 isstored in a persistent store, such as the flash memory 1160, but may bestored in other types of memory devices, such as a read only memory(ROM) or similar storage element. In addition, system software, specificdevice applications, or parts thereof, may be temporarily loaded into avolatile store, such as the random access memory (RAM) 1180.Communications signals received by the mobile device may also be storedin the RAM 1180.

The processing device 1800, in addition to its operating systemfunctions, enables execution of software applications 1300A-1300N on thedevice 1000. A predetermined set of applications that control basicdevice operations, such as data and voice communications 1300A and1300B, may be installed on the device 1000 during manufacture. Inaddition, a personal information manager (PIM) application may beinstalled during manufacture. The PIM may be capable of organizing andmanaging data items, such as e-mail, calendar events, voice mails,appointments, and task items. The PIM application may also be capable ofsending and receiving data items via a wireless network 1401. The PIMdata items may be seamlessly integrated, synchronized and updated viathe wireless network 1401 with corresponding data items stored orassociated with a host computer system.

Communication functions, including data and voice communications, areperformed through the communications subsystem 1001, and possiblythrough the short-range communications subsystem 1020. Thecommunications subsystem 1001 includes a receiver 1500, a transmitter1520, and one or more antennas 1540 and 1560. In addition, thecommunications subsystem 1001 also includes a processing module, such asa digital signal processor (DSP) 1580, and local oscillators (LOs) 1601.The specific design and implementation of the communications subsystem1001 is dependent upon the communications network in which the mobiledevice 1000 is intended to operate. For example, a mobile device 1000may include a communications subsystem 1001 designed to operate with theMobitex™, Data TAC™ or General Packet Radio Service (GPRS) mobile datacommunications networks, and also designed to operate with any of avariety of voice communications networks, such as Advanced Mobile PhoneSystem (AMPS), time division multiple access (TDMA), code divisionmultiple access (CDMA), Wideband code division multiple access (W-CDMA),personal communications service (PCS), GSM (Global System for MobileCommunications), enhanced data rates for GSM evolution (EDGE), etc.Other types of data and voice networks, both separate and integrated,may also be utilized with the mobile device 1000. The mobile device 1000may also be compliant with other communications standards such as 3GSM,3rd Generation Partnership Project (3GPP), Universal MobileTelecommunications System (UMTS), 4G, etc.

Network access requirements vary depending upon the type ofcommunication system. For example, in the Mobitex and DataTAC networks,mobile devices are registered on the network using a unique personalidentification number or PIN associated with each device. In GPRSnetworks, however, network access is associated with a subscriber oruser of a device. A GPRS device therefore typically involves use of asubscriber identity module, commonly referred to as a SIM card, in orderto operate on a GPRS network.

When required network registration or activation procedures have beencompleted, the mobile device 1000 may send and receive communicationssignals over the communication network 1401. Signals received from thecommunications network 1401 by the antenna 1540 are routed to thereceiver 1500, which provides for signal amplification, frequency downconversion, filtering, channel selection, etc., and may also provideanalog to digital conversion. Analog-to-digital conversion of thereceived signal allows the DSP 1580 to perform more complexcommunications functions, such as demodulation and decoding. In asimilar manner, signals to be transmitted to the network 1401 areprocessed (e.g. modulated and encoded) by the DSP 1580 and are thenprovided to the transmitter 1520 for digital to analog conversion,frequency up conversion, filtering, amplification and transmission tothe communication network 1401 (or networks) via the antenna 1560.

In addition to processing communications signals, the DSP 1580 providesfor control of the receiver 1500 and the transmitter 1520. For example,gains applied to communications signals in the receiver 1500 andtransmitter 1520 may be adaptively controlled through automatic gaincontrol algorithms implemented in the DSP 1580.

In a data communications mode, a received signal, such as a text messageor web page download, is processed by the communications subsystem 1001and is input to the processing device 1800. The received signal is thenfurther processed by the processing device 1800 for an output to thedisplay 1600, or alternatively to some other auxiliary I/O device 1060.A device may also be used to compose data items, such as e-mailmessages, using the keypad 1400 and/or some other auxiliary I/O device1060, such as a touchpad, a rocker switch, a thumb-wheel, or some othertype of input device. The composed data items may then be transmittedover the communications network 1401 via the communications subsystem1001.

In a voice communications mode, overall operation of the device issubstantially similar to the data communications mode, except thatreceived signals are output to a speaker 1100, and signals fortransmission are generated by a microphone 1120. Alternative voice oraudio I/O subsystems, such as a voice message recording subsystem, mayalso be implemented on the device 1000. In addition, the display 1600may also be utilized in voice communications mode, for example todisplay the identity of a calling party, the duration of a voice call,or other voice call related information.

The short-range communications subsystem enables communication betweenthe mobile device 1000 and other proximate systems or devices, whichneed not necessarily be similar devices. For example, the short-rangecommunications subsystem may include an infrared device and associatedcircuits and components, a Bluetooth™ communications module to providefor communication with similarly-enabled systems and devices, or a NFCsensor for communicating with a NFC device or NFC tag via NFCcommunications.

Other features relating to communications devices are disclosed inco-pending application(s) “QUADRATURE COMMUNICATIONS DEVICE WITH IANTENNAS AND Q ANTENNAS AND MODULATED POWER SUPPLY AND RELATED METHODS,”Ser. No. 13/049,200; and “QUADRATURE COMMUNICATIONS DEVICE WITH IANTENNAS AND Q ANTENNAS AND RELATED METHODS,” Ser. No. 13/049,243, allincorporated herein by reference in their entirety.

Many modifications and other embodiments will come to the mind of oneskilled in the art having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it isunderstood that various modifications and embodiments are intended to beincluded within the scope of the appended claims.

That which is claimed is:
 1. A communications device comprising: aplurality of In-phase (I) power amplifiers configured to generate aplurality of I amplified signals; a plurality of Quadrature (Q) poweramplifiers configured to generate a plurality of Q amplified signals; afirst phase shifter coupled upstream of said plurality of I poweramplifiers; a second phase shifter coupled upstream of said plurality ofQ power amplifiers; an I controller coupled to said plurality of I poweramplifiers and configured to selectively enable at least one of saidplurality of I power amplifiers based upon at least a selected outputpower and to control said plurality of I power amplifiers to modulateand mix an I carrier signal directly received from said first phaseshifter with an I digital baseband signal to generate the plurality of Iamplified signals; a Q controller coupled to said plurality of Q poweramplifiers and configured to selectively enable at least one of saidplurality of Q power amplifiers based upon at least a selected outputpower and to control said plurality of Q power amplifiers to modulateand mix a Q carrier signal directly received from said second phaseshifter with a Q digital baseband signal to generate the plurality of Qamplified signals; a power combiner configured to combine the pluralityof I amplified signals and the plurality of Q amplified signals in acombined amplified signal; and an antenna coupled to said powercombiner.
 2. The communications device of claim 1 further comprising anI digital-to-analog converter (DAC) configured to generate an I biascurrent signal for said plurality of I power amplifiers, and a Q DACconfigured to generate a Q bias current signal for said plurality of Qpower amplifiers.
 3. The communications device of claim 2 furthercomprising an I look-up table (LUT) module upstream of said I DAC andconfigured to supply a linear I signal thereto, and a Q LUT moduleupstream of said Q DAC and configured to supply a linear Q signalthereto.
 4. The communications device of claim 1 further comprising aphase locked loop (PLL) configured to generate the I and Q carriersignals.
 5. The communications device of claim 4 wherein said PLL isconfigured to generate the I and Q carrier signals comprising constantenvelop I and Q carrier signals.
 6. A communications device comprising:a plurality of In-phase (I) pre-amplifiers configured to generate aplurality of I amplified signals; a plurality of Quadrature (Q)pre-amplifiers configured to generate a plurality of Q amplifiedsignals; a first phase shifter coupled upstream of said plurality of Ipre-amplifiers; a second phase shifter coupled upstream of saidplurality of Q pre-amplifiers; an I controller coupled to said pluralityof I pre-amplifiers and configured to selectively enable at least one ofsaid plurality of I pre-amplifiers based upon at least a selected outputpower and to control said plurality of I pre-amplifiers to modulate andmix an I carrier signal directly received from said first phase shifterwith an I digital baseband signal to generate the plurality of Iamplified signals; a Q controller coupled to said plurality of Qpre-amplifiers and configured to selectively enable at least one of saidplurality of Q pre-amplifiers based upon at least a selected outputpower and to control said plurality of Q pre-amplifiers to modulate andmix a Q carrier signal directly received from said second phase shifterwith a Q digital baseband signal to generate the plurality of Qamplified signals; a phase locked loop (PLL) configured to generate theI and Q carrier signals for said pluralities of I and Q pre-amplifiers;a power combiner configured to combine the plurality of I amplifiedsignals and the plurality of Q amplified signals in a combined amplifiedsignal; and an antenna coupled to said power combiner.
 7. Thecommunications device of claim 6 further comprising an Idigital-to-analog converter (DAC) configured to generate an I biascurrent signal for said plurality of I pre-amplifiers, and a Q DACconfigured to generate a Q bias current signal for said plurality of Qpre-amplifiers.
 8. The communications device of claim 7 furthercomprising an I look-up table (LUT) module upstream of said I DAC andconfigured to supply a linear I signal thereto, and a Q LUT moduleupstream of said Q DAC and configured to supply a linear Q signalthereto.
 9. The communications device of claim 6 wherein said PLL isconfigured to generate the I and Q carrier signals comprising constantenvelop I and Q carrier signals.
 10. A method of operating acommunications device comprising: using a plurality of In-phase (I)power amplifiers to generate a plurality of I amplified signals; using aplurality of Quadrature (Q) power amplifiers to generate a plurality ofQ amplified signals; using an I controller to selectively enable atleast one of the plurality of I power amplifiers based upon at least aselected output power and to control the plurality of I power amplifiersto modulate and mix an I carrier signal directly received from a firstphase shifter with an I digital baseband signal to generate theplurality of I amplified signals; using a Q controller to selectivelyenable at least one of the plurality of Q power amplifiers based upon atleast a selected output power and to control said plurality of Q poweramplifiers to modulate and mix a Q carrier signal directly received froma second phase shifter with a Q digital baseband signal to generate theplurality of Q amplified signals; using a power combiner to combine theplurality of I amplified signals and the plurality of Q amplifiedsignals in a combined amplified signal; and using an antenna to transmitthe combined amplified signal.
 11. The method of claim 10 furthercomprising using an I digital-to-analog converter (DAC) to generate an Ibias current signal for the plurality of I power amplifiers, and using aQ DAC to generate a Q bias current signal for the plurality of Q poweramplifiers.
 12. The method of claim 11 further comprising using an Ilook-up table (LUT) module upstream of the I DAC to supply a linear Isignal thereto, and a Q LUT module upstream of the Q DAC to supply alinear Q signal thereto.